Keeping pace with advancement in multi-media technology, ink-jet printers are widely employed in both fields of professional use and public use. Ink-jet printers are advantageous in various aspects such that they can readily be multi-colored and can readily be expanded in image size, and that they require only a low printing cost. In particular, ink-jet printers using a water-base ink, which is less causative of environmental and safety problems as compared with an oil-base ink, form the mainstream of recent printers.
The ink-jet printers are widely used also as a means for obtaining a hard copy which includes processed image as well as character information. Thus there is a growing need for finer image after the printing.
Fineness of the image is governed by drying property of an ink applied on a recording medium. In a continuous printing onto a plurality of recording media for example, one recording medium previously printed may be overlaid with another recording medium. If an ink on the previously printed recording medium dries insufficiently, the ink may be caught by the overlaid recording medium, which result in a stained image.
One popular method for enhancing the image fineness is such that using a recording medium which comprises a base layer made of synthetic paper, plastic film or pulp paper and an ink accepting layer coated thereon containing a hydrophilic resin or inorganic fine powder (Japanese Laid-Open Patent Publications Nos. 3-82589 and 9-216456). While the method is successful in yielding a high-definition image when the ink discharge is relatively small, the method may cause insufficient drying of the ink when the discharge is relatively large. Increasing the thickness of the coated layer, which is one proposed countermeasure for such problem, will raise the cost and thus ruin the practicability as an ink-jet recording medium.
Another proposal relates to an ink-jet recording medium in which an ink accepting layer mainly composed of a hydrophilic resin is formed by the heat lamination process or the extrusion lamination process (Japanese Laid-Open Patent Publications 8-12871, 9-1920 and 9-314083. Such ink-jet recording medium has also been unsatisfiable since the medium cannot produce thereon a desirable image when the ink discharge is relatively large.
It is therefore an object of the present invention to provide a porous resin film and an inexpensive recording medium using thereof which can ensure rapid drying of the ink, for example, in ink-jet printing and thus can produce thereon a desirable image even when the ink discharge is relatively large.